Author: Robbins

Encountering Caverns in France: TBM Tunneling in Karst Conditions

France’s recently completed Galerie des Janots featured some unexpected challenges: Karst cavities large and small were found throughout the bore as well as two large, uncharted caverns. During excavation with a Main Beam TBM, crews encountered an 8,000 cubic meter cavern studded with stalagmites and a 4,500 cubic meter cavity directly below the bore path. How did the crew overcome the conditions and continue past the voids?

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NASTT No-Dig

Event Name: NASTT No-Dig
Dates: April 5-June 30
Location: Virtual Event
Booth: 2015

Come join us for some (virtual) fun in the sun at NASTT No-Dig’s virtual exhibit hall. Stop by the Robbins booth to meet with our expert staff and found out the latest about our SBU products and projects.

 

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ITA Tunnelling Awards

Event Name: ITA Tunnelling Awards
Dates: December 3-4
Location: Virtual Event

Register for the ITA Tunnelling Awards, a complimentary event to learn about and celebrate the industry’s innovative projects and products worldwide. Stop by the Robbins booth for a live chat with our in-booth experts over video or IM, and get the latest updates on our offerings and events. The virtual exhibition is open during the entire event. We hope to see you there!

Live Awards Ceremony
2 PM CET

 

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TBM Tunneling in Karst Conditions

France’s recently completed Galerie des Janots was the scene of some unforeseen challenges.  During excavation with a Main Beam TBM, crews encountered a stalagmite studded 8,000 cubic meter cavern, and also a 4,500 cubic meter cavity directly under the bore path. In addition to the two large and uncharted caverns, there were also karst cavities of a multitude of sizes found throughout boring. What exactly did the crew do to beat the odds and power through?

For the answer, be sure to listen in as Detlef Jordan, Robbins Sales Manager Europe, goes into detail about the obstacles, lessons learned, and recommendations for future tunnels in karst conditions.

Watch the Recording

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48 Fault Zones and 26 Bar Pressure: Boring Turkey's Gerede Water Transmission Tunnel

Difficult ground doesn’t begin to describe the challenges overcome at a recent tunnel in central Turkey. The breakthrough of a 5.5 m diameter Robbins Crossover XRE TBM at the Gerede Water Transmission Tunnel was a feat of modern construction.

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Robbins Main Beam carves out a win in Louisville

A 6.5 km (4 mi) long tunnel for wastewater storage below Louisville, Kentucky, USA has more to it than meets the eye.  “At first glance, this seems like a straightforward project, but it turned out to be much more challenging,” said Shemek Oginski, Project Manager for the contractor, a joint venture of Shea/Traylor. The 6.7 m (22 ft) diameter Robbins Main Beam TBM and conveyor system had to cope with overstress in the crown that resulted in significant rock fallout in seven different areas, as well as methane gas in the tunnel.  By the machine’s breakthrough on September 22, 2020, the crew had much to celebrate.

The machine was refurbished and consisted of older components as well as a brand new cutterhead supplied by Robbins and completely rebuilt electrical and hydraulic systems. “This was definitely an older machine—I actually operated it on the DART [Dallas Area Rapid Transit] tunnels in Dallas, Texas in the 1990s, but with many of the components being new we were confident in it,” said Oginski.

The original tunnel was expected to be 4 km (2.5 mi) long, but a change order added to the length by 2.1 km (1.3 mi). The extension was ordered by the owner, Louisville Metropolitan Sewer District (MSD), and its Engineer-of-Record Black & Veatch in order to eliminate four surface CSO storage basins. That included one basin originally located at the site of the TBM breakthrough, explains Oginski: “The original CSO site was located in close proximity to Beargrass Creek and had flooded multiple times. It was decided to extend the tunnel to that site in order to use the tunnel as storage instead, and connect it to the sewer system.”  MSD installed a sheeting wall to protect the site from floodwaters while Shea-Traylor installed liner plate in the retrieval shaft, resulting in a site that is in much better shape.

It was in the 2.1 km (1.3 mi) extension, essentially a bifurcation of the main tunnel, where the crew encountered much of the crown overstress. “The longest section of overstress was 700 m (2,300 ft) and took two and a half months to get through,” said Oginski.  The crew switched up the prescribed rock bolt pattern of four to six bolts at 1.5 m (5.0 ft) centers, and instead installed six bolts at 1 m (3 ft) centers. “It worked out to two rows per push. When that wasn’t enough, we installed wire mesh in the crown, mine straps, and channels.  It definitely took extra time to install steel support, remove loose rock, and deal with the rock coming down so we could install rock support safely.” Overbreak varied from a few inches above the machine to 30 cm (1 ft) or more.

“We also had encountered natural methane gas in the tunnel just shortly before holing through,” said Oginski.  The methane was discovered while the crew were probing out 150 ft ahead of the machine—something that the crew did continuously throughout the bore, using one, two or four probe holes depending on the geology. “We were down for about two weeks and were able to contain the methane within the cutterhead, where concentration spiked at 100% LEL. We were able to resume work after systematically ventilating, probing and grouting multiple times.”

Despite the challenges, the TBM was able to achieve up to 658 m (2,159 ft) in one month and 192 m (630 ft) in one week. The Robbins conveyor, including a 68.6 m (225 ft) long vertical belt, made this progress achievable, said Oginski: “The conveyor is definitely the way to go, especially for longer drives. There was quite a difference in performance between the extension tunnel, which we mined with lift-boxes, and mining with the conveyor.  Our best month in the extension tunnel with the boxes was 221 m (725 ft), so that is a big difference.”

With tunneling now complete, Oginski is “definitely proud that we got to the end, as this is a challenging project.” The contractor is removing the components of the TBM to be stored in their yard in Mt. Pleasant, PA, and sees future applications for the equipment. “If the right project comes up then yes, it’s likely we would use this machine again.”

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HYDRO 2020

Event Name: Hydro 2020
Dates: October 26-28
Location: Virtual Event

Register for the Hydro 2020 online event and get access to the latest information on all things hydropower, include Robbins’ innovative approach to small hydro tunnels at steep inclines using small diameter tunneling machines. Hear Robbins Civil Engineer and Cutter Product Manager Sindre Log speak on the use of three unique machines at up to 45 degree inclines in Norway.

Presentation Details:

Tuesday October 27
Session 22 – Tunnels & Underground Works – 2
11:00AM – 12:30PM CET
Title: Small but Powerful: Compact Hydro Tunneling offers Renewable Energy Solutions

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Boring Through 48 Fault Zones and 26 Bar Pressure

Difficult ground doesn’t begin to describe the challenges overcome at a recent tunnel in central Turkey. The breakthrough of a 5.5 m diameter Robbins Crossover XRE TBM at the Gerede Water Transmission Tunnel was a feat of modern construction. The 9 km leg was the final section of the 31.6 km long water supply line bored through what is widely considered to be Turkey’s most challenging geology: from 48 fault zones to water pressures up to 26 bar, the ground put the machine and the crew to the test.

Listen in on the conversation with Robbins Vice President Doug Harding as we find out how the unique TBM design and experienced crew overcame a gamut of challenges.

Watch the Video

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Hybrid TBM Excavation in Challenging Mixed Ground Conditions at the Mumbai Metro

Excavation in mixed ground conditions is always a challenge, but under a densely urban environment the stakes become even higher. At India’s Mumbai Metro, two 6.65 m hybrid-type rock/soft ground Single Shield TBMs are successfully boring parallel 2.8 km tunnels in basalt rock with transition zones of shale, tuff, and breccia below the city. They have made intermediate breakthroughs at the 1.2 km mark and overcome rock strengths up to 125 MPa UCS with significant water ingress, all just one year after factory acceptance, shipping, site assembly, and launch. The hybrid machines are optimized for abrasive rock geology using a robust cutterhead mounted with disc cutters and a reinforced screw conveyor at the centerline. The machines can also operate in closed or semi-closed mode using features designed to advance in soft ground with water inflows: dual ratio gearboxes to adjust cutterhead speed and torque to the geology, screw conveyors with bulkhead gates and discharge gates, ground conditioning with foam and polymers, and probe drills for pre-excavation grouting.

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TBM Excavation in Himalayan Geology: Over 1,200 Meters per Month at the Bheri Babai Diversion Multipurpose Project

A Double Shield TBM achieved in 17 months what was projected to have taken 12 years with Drill & Blast: The 12.2 km long Bheri Babai Diversion Multipurpose Project (BBDMP).  Bored in Himalayan geology including sandstone, mudstone, and conglomerate, the excavation was able to achieve over 1,200 m advance per month on multiple occasions.   Crews achieved this while traversing a fault zone and getting through one section that required a bypass tunnel constructed in just five days. The success of this tunnel is not only in breaking through a historically difficult mountain range, but also in changing the notion, to the people of Nepal, that drill and blast is the way to excavate mountainous rock tunnels.

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